I have never understood it. When I have pulseaudio running many processes which try to play music stop, because they are waiting for the sound device to become idle. This was also the reason why Gnome could not be able to login.
When using FreeBSD I even switch all this Linux daemon crap off. OSS can do audio mixing natively and I have never had problems with it... I even did not know about all the problems which exist on Linux with all these audio daemons. This seems to be a total mess.